If you’ve got bulges, wrinkles, or sagging cloth, it’s going to make your outline look sloppy. On a large man, the effect gets amplified, and it looks even worse. Many large men dress in clothes that are several sizes too big, thinking they are disguising their physique. But baggy clothes don’t fool anyone and in fact draw more attention to your weight while downgrading your overall appearance and the impression you make.
There’s also a simple comfort issue here: the better the fit, the more comfortable your clothes feel, which is good for your mood and for your appearance. So your first consideration with any garment should always be the fit. You want the cloth to rest lightly on your body — not hugging it tight and not hanging off your skin with visible folds of extra cloth.